From 9c1c2b35f1d94de8325344c2777d7ee67492db3b Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 3 Apr 2019 13:16:01 -0400 Subject: [PATCH] ceph: hold extra reference to r_parent over life of request Currently, we just assume that it will stick around by virtue of the submitter's reference, but later patches will allow the syscall to return early and we can't rely on that reference at that point. While I'm not aware of any reports of it, Xiubo pointed out that this may fix a use-after-free. If the wait for a reply times out or is canceled via signal, and then the reply comes in after the syscall returns, the client can end up trying to access r_parent without a reference. Take an extra reference to the inode when setting r_parent and release it when releasing the request. Cc: stable@vger.kernel.org Signed-off-by: Jeff Layton Reviewed-by: "Yan, Zheng" Signed-off-by: Ilya Dryomov --- fs/ceph/mds_client.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c index 374db1bd57d1..145d46ba25ae 100644 --- a/fs/ceph/mds_client.c +++ b/fs/ceph/mds_client.c @@ -708,8 +708,10 @@ void ceph_mdsc_release_request(struct kref *kref) /* avoid calling iput_final() in mds dispatch threads */ ceph_async_iput(req->r_inode); } - if (req->r_parent) + if (req->r_parent) { ceph_put_cap_refs(ceph_inode(req->r_parent), CEPH_CAP_PIN); + ceph_async_iput(req->r_parent); + } ceph_async_iput(req->r_target_inode); if (req->r_dentry) dput(req->r_dentry); @@ -2676,8 +2678,10 @@ int ceph_mdsc_submit_request(struct ceph_mds_client *mdsc, struct inode *dir, /* take CAP_PIN refs for r_inode, r_parent, r_old_dentry */ if (req->r_inode) ceph_get_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN); - if (req->r_parent) + if (req->r_parent) { ceph_get_cap_refs(ceph_inode(req->r_parent), CEPH_CAP_PIN); + ihold(req->r_parent); + } if (req->r_old_dentry_dir) ceph_get_cap_refs(ceph_inode(req->r_old_dentry_dir), CEPH_CAP_PIN);